[Introspection] Wrong relation type when introspecting on PostgreSQL from Prisma V1

Bug description

I’m trying to migrate from Prisma1 to Prisma2 (brownfield) but I encounter a problem with introspection.

A relation between two of my types (User and Payout) is “translated” into a 1:m relation instead of 1:1 .

How to reproduce

Here is my SQL (Postgresql) schema created by Prisma V1 the first time where I deployed the service :

CREATE TABLE "default$default"."User"
(
    id character varying(25) COLLATE pg_catalog."default" NOT NULL,
    isActive boolean NOT NULL,
    CONSTRAINT "User_pkey" PRIMARY KEY (id)
)

CREATE TABLE "default$default"."Payout"
(
    id character varying(25) COLLATE pg_catalog."default" NOT NULL,
    user character varying(25) COLLATE pg_catalog."default",
    CONSTRAINT "Payout_pkey" PRIMARY KEY (id),
    CONSTRAINT "Payout_user_fkey" FOREIGN KEY ("user") REFERENCES "default$default"."User" (id) MATCH SIMPLE
)

I kept the most important columns only. As you can see, there is no UNIQUE attribute on User.id or Payout.id columns).

My datamodel (Prisma1) :

type User {
  id: ID! @id
  isActive: Boolean! @default(value: true)
  payout: Payout @relation(name: "UserOnPayout", onDelete: CASCADE)
}

type Payout {
  id: ID! @id
  user: User @relation(link: INLINE, name: "UserOnPayout", onDelete: SET_NULL)
}

If I Introspect the database with the prisma introspect command (Prisma1), everything works fine but when I introspect with Prisma2 (npx prisma2 introspect with the latest alpha or preview024 version), I have the following datamodel with a 1:m relation:

model User {
  id                        String                      @id
  isActive                  Boolean
  payout                    Payout[]
}

model Payout {
  id                     String       @id
  user                   User?
}

What am I doing wrong ?

Expected behavior

I was expecting the following Prisma2 schema:

model User {
  id                        String                      @id
  isActive                  Boolean
  payout                    Payout?
}

model Payout {
  id                     String       @id
  user                   User?
}

Environment & setup

• OS: Ubuntu 18.04 LTS
• Database: PostgreSQL in Docker (image: postgres:10.3)
• Prisma1 version: prisma@1.34.10
• Prisma2 version: prisma2@2.0.0-preview024
• Node.js version: 8.16.0

[janpio]

FYI: This will be tackled via a later iteration of https://github.com/prisma/prisma/issues/1937

[janpio]

Should be solved via https://www.prisma.io/docs/guides/upgrade-guides/upgrade-from-prisma-1